LAUSR

A tiny group of neurons in the brainstem matches breathing rate to the level of calmness versus arousal. The calming effect of breathing The rhythmic activity of a cluster of neurons in the brainstem initiates breathing. This cluster is composed of distinct, though intermingled, subgroups of neurons. Yackle et al. found a small, molecularly defined neuronal subpopulation in this breathing rhythm generator that directly projects to a brain center that plays a key role in generalized alertness, attention, and stress (see the Perspective by Sheikbahaei and Smith). Removal of these cells did not affect normal breathing but left the animals unusually calm. The breathing center thus has a direct and dramatic influence on higher-order brain function. Science, this issue p. 1411; see also p. 1370 Slow, controlled breathing has been used for centuries to promote mental calming, and it is used clinically to suppress excessive arousal such as panic attacks. However, the physiological and neural basis of the relationship between breathing and higher-order brain activity is unknown. We found a neuronal subpopulation in the mouse preBötzinger complex (preBötC), the primary breathing rhythm generator, which regulates the balance between calm and arousal behaviors. Conditional, bilateral genetic ablation of the ~175 Cdh9/Dbx1 double-positive preBötC neurons in adult mice left breathing intact but increased calm behaviors and decreased time in aroused states. These neurons project to, synapse on, and positively regulate noradrenergic neurons in the locus coeruleus, a brain center implicated in attention, arousal, and panic that projects throughout the brain.